APPARATUS TO PREVENT MISMEASURING OF WALL THICKNESS GAUGING BY ULTRASOUND

摘要

Method and apparatus are disclosed for preventing mismeasurement when gauging wall thickness by an ultrasonic pulse echo transit time method using separate transmitter and receiver probes. The pulse transit time, in the specimen plus a fixed known period of time is taken as the gauging value. Cross talk, i.e., an echo from the probe-to-specimen interface, is prevented from causing mismeasurements of thin wall specimens by providing an electronic gate which is opened during the cross talk time interval for receiving cross talk pulses having an amplitude over a predetermined lower threshold value to actuate a mismeasurement warning light or to prevent the gauge from indicating wall thickness.